1. Field of the Invention
The invention relates to a direction and speed control device, more particularly to a direction and speed control device for an electronic wheelchair.
2. Description of the Related Art
A conventional direction control device for an electronic wheelchair includes a control stick that is manually operated to actuate switches, thereby resulting in signals provided to a controller for controlling moving direction of the electronic wheelchair. However, since the switches are only capable of providing indication of a desired direction and are not capable of indicating extent of movement of the control stick, control of the electronic wheelchair for making slight turns is not possible.
Referring to FIG. 1, another conventional electronic wheelchair 1 includes a direction controller 11 for sending signals to a driving control unit (not shown) to control driving operation of a wheel driving unit (not shown) in order to control in turn moving direction of the electronic wheelchair 1. With further reference to FIG. 2, the direction controller 11 includes a hollow base member 111, a circuit board 112 disposed in the base member 111, four angularly spaced apart lower sensing coils 113 disposed on the circuit board 112, a control stick 114 that extends pivotably through the base member 111 and that is disposed above and spaced apart from the circuit board 112, an upper sensing coil 115 mounted on a bottom end of the control stick 114, and a restoring spring 116 for biasing the control stick 114 to an initial non-operated position. The circuit board 112 generates direction signals corresponding to tilt of the upper sensing coil 115 relative to the lower sensing coils 113.
In operation, when a top end of the control stick 114 is pushed forward, the upper sensing coil 115 on the bottom end of the control stick 114 moves rearward relative to the lower sensing coils 113 on the circuit board 112, thereby enabling the circuit board 112 to generate a forward direction signal for driving forward movement of the electronic wheelchair 1. On the other hand, when the top end of the control stick 114 is pushed rearward, the upper sensing coil 115 on the bottom end of the control stick 114 moves forward relative to the lower sensing coils 113, thereby enabling the circuit board 112 to generate a rearward direction signal for driving rearward movement of the electronic wheelchair 1. The circuit board 112 generates one of left and right direction signals in the same manner upon pushing the control stick 114 to the left or to the right.
Through such design, the circuit board 112 is able to generate appropriate direction signals corresponding to magnitude and direction of tilt of the upper sensing coil 115 relative to the lower sensing coils 113 so that control of the electronic wheelchair 1 for making slight turns is possible.
However, in the conventional electronic wheelchair 1, the power output of the wheel driving unit is not adjusted to correspond to actual road conditions. In particular, the power output of the wheel driving unit is not increased when the electronic wheelchair 1 is moving uphill and is not reduced when the electronic wheelchair 1 is moving downhill. Moreover, use of the sensing coils 115, 113 results in a bulky design and complicates the manufacturing process.